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The students used a sorting board like this.
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They worked in pairs to sort their flash cards into piles. Their teacher gave them a Subtraction Facts I Know chart to keep track of their progress. After several days, the students discussed their progress.
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Self-Check: Subtraction Facts I Know
With your partner, sort your subtraction flash cards on the Sorting Flash Cards Board. Use your Subtraction Facts I Know chart to record your progress. All these tools are in your Student Activity Book.